8-Hydroxyquinoline (8HQ Substrates)

8-Hydroxyquinoline (8HQ) based substrates give a non-diffuse black pigmentation following hydrolysis in the presence of a ferric salt, due to the subsequent chelate formed between the release 8-HQ and ferric ions. 8HQ substrates do have limitations as they show some toxicity to gram-positive bacteria. 8-Hydroxyquinoline beta-D-glucopyranoside (Product code 35059) has been shown to be effective for the detection of beta-glucosidase activity in a number of species of Enterobacteriaceae. This substrate could potentially be used in chromogenic media targeted at Gram-negative bacteria, e.g. for the indirect detection of Salmonella spp.